Fork crown for a bicycle

Abstract

The invention relates to a fork crown for a bicycle, comprising a central portion (1) in which a central duct (2) is formed, and two lateral arms (4) each having a distal portion (5) comprising a lateral duct (6), the lateral and central ducts extending along a vertical axis, each opening into apertures (2a, 2b, 6a, 6b) formed respectively in the upper and lower faces (7b) of the fork crown, the faces being separated by a thickness of material measured in a vertical direction, at least one cavity (16i, 16m, 16e) being arranged between two vertically opposite zones of one face (7b), having an opening (17i, 17m, 17e) formed in one of the zones and extending over a depth measured in a vertical direction which is less than 80% of the thickness between the zones.

Description

[0001] DESCRIPTION

[0002] Bicycle fork crown

[0003] The invention relates to a bicycle fork crown, as well as a bicycle fork comprising such a fork crown.

[0004] Bicycle forks are known to have a central part in which a central channel for receiving a pivot of the fork is formed, and two arms, formed in one piece, which extend laterally on either side of said central part, each presenting a distal portion carrying a lateral channel for receiving a leg of the fork.

[0005] To be able to withstand the significant mechanical stresses to which fork yokes are subjected in use, it is known to manufacture them from metallic material by machining, mechanical welding, stamping and / or forging.

[0006] Implementing these processes has the drawback of requiring a significant cycle time, which increases the manufacturing cost of the fork crowns. Furthermore, the use of metallic materials, such as steel or aluminum alloys, impacts the weight of the fork crown, and therefore the overall weight of the bicycle.

[0007] Document EP-4 227 198 describes a fork tee made of a metal alloy, including aluminum, using various processes including forging, computer-aided design (CAD) manufacturing or casting.

[0008] In particular, the triple clamp features bores that can be formed in the front face of each arm, along a horizontal direction perpendicular to the axis of the ducts. These bores improve the aerodynamics of the triple clamp and reduce its weight, while ensuring sufficient resistance to mechanical stresses. This arrangement is not entirely satisfactory, as the bore configuration is not suitable for simple manufacturing of the triple clamp, especially by pressure injection molding of an aluminum alloy.

[0009] The invention aims to improve the prior art by proposing a bicycle fork designed to have both a reduced weight and sufficient strength to withstand the required mechanical stresses, while being easy to manufacture, in particular by injection molding of a metallic material (“high pressure die casting” in English).

[0010] To this end, according to a first aspect, the invention proposes a bicycle fork crown, comprising a central part in which is formed a central channel for receiving a pivot of said fork and, formed in one piece, two arms extending laterally on either side of said central part, each of said arms having a distal portion carrying a lateral channel for receiving a leg of said fork, said lateral and central channels extending along a vertical axis, each opening into orifices formed in the respective upper and lower faces of said fork crown, said faces being separated by a thickness of material measured along a vertical direction, said fork crown having at least one cavity which is disposed between two vertically opposed zones of respectively one face,said cavity having an opening formed in one of said zones and extending over a depth measured in a vertical direction which is less than 80% of the thickness between said zones.

[0011] According to a second aspect, the invention proposes a bicycle fork comprising such a fork crown, in which a pivot is fixed in the central conduit above the upper face, and two legs are fixed in respectively a lateral conduit below the lower face.

[0012] Other features and advantages of the invention will become apparent in the following description, made with reference to the attached figures, in which: [Fig.1] partially represents in perspective from below a bicycle fork equipped with a tee according to an embodiment of the invention;

[0013] [Fig.2] and

[0014] [Fig.3] represent, respectively in front view and in perspective view from below, the fork tee of figure 1,

[0015] [Fig.3a] being an enlarged view of the right part of figure 3;

[0016] [Fig. 4] and

[0017] [Fig. 5] represent the fork tee of the previous figures, respectively in perspective top view and along two different longitudinal and vertical cutting planes,

[0018] [Fig.4a] and

[0019] [Fig.5a] being enlarged views of the right part of respectively figure 4 and figure 5.

[0020] In relation to these figures, a bicycle fork crown is described below, as well as a bicycle fork comprising such a crown.

[0021] Advantageously, the fork crown is manufactured by high-pressure die casting of an aluminum alloy, in particular chosen from the AISilOMnMg alloy and the EN AC 43500 alloy, due to their good ability to be molded in this way and their resistance suitable to withstand the mechanical stresses borne by the fork crowns.

[0022] This alloy can also be subjected to suitable heat treatment, particularly after the manufacture of the fork crown, in order to give the latter improved mechanical properties, depending on the type of bicycle to be equipped with said crown.

[0023] The fork tee comprises a central part 1 in which is formed a central conduit 2 for receiving a pivot 3 of the fork, and, formed in one piece with said central part, two arms 4 which extend laterally on either side of it, each presenting a distal portion 5 carrying a lateral conduit 6 for receiving a leg 8 of said fork.

[0024] The lateral ducts 6 and central 2 extend along a vertical axis V, each opening into orifices 2a, 2b, 6a, 6b formed in the upper 7a and lower 7b faces respectively of the fork tee.

[0025] In the description, the terms for positioning in space are taken with reference to the vertical position of the fork tee as shown in Figure 2. Thus:

[0026] - the terms "horizontal", "vertical", "superior" and "inferior" are taken in relation to the vertical axis V;

[0027] - the terms "longitudinal" and "transverse" are taken in reference to a maximum dimension of the fork tee, and refer to directions respectively parallel and perpendicular to this maximum dimension;

[0028] - the terms "front" and "rear" are taken in reference to the direction of travel of a bicycle equipped with a fork crown.

[0029] As shown in Figure 1, the bicycle fork includes a pivot 3 which is fixed in the central conduit 2 and above the upper face 7a, and two legs 8 which are fixed in a lateral conduit 6 below the lower face 7b.

[0030] The pivot 3 comprises a tubular body 9, the lower end of which is fixed in the central conduit 2, said body being intended to be mounted for rotation in a steering tube formed for this purpose at the front of a bicycle frame.

[0031] In relation to the telescopic fork shown, each of the legs 8 comprises a plunger 10 formed of a tubular body whose upper end is fixed in a lateral conduit 6, and a damping sleeve 11 in which said plunger is mounted in translation. The sleeves 11 are connected at their upper ends by an inverted U-shaped arch 12 which is offset forwards so as not to contact the fork crown during damping movements, and each has a lower end provided with a notch 13 to allow the reversible mounting of a front wheel hub.

[0032] As shown in particular in figures 2, 4 and 5, the upper face 7a - respectively lower face 7b - has an arcuate section which extends between the upper orifices 6a - respectively lower orifices 6b - of the lateral conduits 6. In particular, the section of the upper face 7a has a convexity, and the section of the lower face 7b has a concavity.

[0033] The orifices 6a, 6b of the lateral conduits 6 are each surrounded by a flat surface 14, in order to provide material around the portion of tube 9, 10 fixed inside each of said lateral conduits. The upper orifice 2a of the central conduit 2 is surmounted by a base 15 intended to surround the portion of the pivot 3 fixed in said central conduit.

[0034] In relation to figures 2 to 5, the central conduit 2 has a vertical and transverse plane T of symmetry, the arms 4 extending longitudinally on either side of said vertical plane.

[0035] In the description, the terms "internal" and "external" are taken with reference to this vertical plane T, and refer to positions respectively close to and far from this plane T.

[0036] Advantageously, the fork tee is symmetrical with respect to the vertical plane T.

[0037] The upper face 7a and lower face 7b of the fork tee are separated by a thickness of material E measured in a vertical direction. Referring to Figure 5, the thickness E is substantially constant along the lateral arms 4 of the fork tee. The fork tee has at least one cavity 16i, 16 m 16 e which is arranged between two vertically opposed zones of respectively a face 7a, 7b, said cavity having an opening 17\, 17 m 17 e formed in one of said zones and extending over a depth Pi, P m, Pe measured along a vertical direction which is less than 80% of the thickness E between said zones.

[0038] Such a cavity 16i, 16 m 16 e allows the thickness E of the fork crown to be reduced in an area where the mechanical stresses experienced by said crown are reduced, thus lightening its overall weight without compromising its mechanical strength. Furthermore, the vertical arrangement of cavity 16i, 16 m 16 e makes it easier to manufacture the fork crown by molding, and in particular its axial demolding.

[0039] In the embodiment shown, the fork tee comprises two sets of cavities 16i, 16 m 16 e arranged symmetrically on either side of the vertical plane T, the opening 17, 17 m 17 e of each cavity 16i, 16 m 16 e being formed respectively in a zone of the lower face 7b.

[0040] Each assembly has an internal group of at least one cavity 16i whose opening 17\ extends across the central part 1 and the adjacent arm 4.

[0041] In relation to figures 3, 3a, 4 and 4a, each internal group comprises two cavities 16i whose openings 17\ are separated along a transverse direction D.

[0042] The two internal cavities 16i of the same group are symmetrical with respect to a longitudinal plane L, corresponding to the cross-sectional plane of Figures 4 and 4a, and each has an opening 17 with a generally triangular, specifically equilateral, geometry, the apex of which 23 is oriented towards the interior of the fork tee. Each assembly also has a central group of at least one cavity 16m with an opening 17 m is formed on the corresponding arm 4.

[0043] In the figures, each central group comprises a single cavity 16 m including the opening 17 mis positioned longitudinally in the middle part of arm 4. In particular, each central opening 17 m presents a pentagonal geometry with one vertex 18 oriented towards the central conduit 2.

[0044] Advantageously, each of the internal cavities 16i has a border that is positioned opposite a border of cavity 16 m by defining between them a stiffening rib 24 which makes the transfer of force by the fork yoke more reliable.

[0045] In particular, the two ribs 24 thus formed intersect in the longitudinal plane L, being inclined relative to the vertical plane T in the direction of the corresponding lateral conduit 6, for example at an angle between 20° and 60°, preferably between 40° and 55°. Furthermore, the minimum width of the ribs 24 measured between the edges of the cavities 16i, 16 m is at least equal to 25% of the maximum dimension of the openings 17i, 17 mof said cavities, for example being between 6 mm and 10 mm, advantageously of the order of 9 mm.

[0046] Each assembly also features an external group of at least one cavity 16 e including the opening 17 e is formed on arm 4 and near the corresponding lateral conduit 6.

[0047] In relation to Figures 1, 3, 3a and 4, each external group comprises a single cavity 16 e including the opening 17 e is positioned in the front part of arm 4, the pentagonal opening 17 m of the central cavity 16 m presenting a side 19 which is oriented transversely towards said external opening. Furthermore, each external opening 17 e presents a roughly cylindrical geometry which defines, with one edge of the central cavity, 16 m a rib 25 for stiffening the fork crown. Advantageously, each cavity 16i, 16 m 16 efeatures a radial border 20 for connection with its opening 1 Zi, 17 m , 17th which is formed by the cavity molding formation matrix.

[0048] Furthermore, each opening 17i, 17 m 17 e presents a maximum dimension which is large enough to allow the fork tee to be demolded, said maximum dimension being between 50% and 150% of the cavity depth.

[0049] Each cavity 16i, 16 m 16 e It also features a well 21 i, 21 m 21 e whose periphery extends generally vertically to a bottom 22i, 22 m 22 e .

[0050] As shown in figures 4, 4a, 5 and 5a, each background 22i, 22 m 22 e extends roughly parallel to the area of ​​face 7a opposite the opening 17i, 17m, 17 e of cavity 16i, 16 m 16e corresponding (i.e., the upper face), so as to form a thickness ei, e m , e e substantially constant between said base and said upper face.

[0051] In the embodiment shown, the central cavities 16 m and external 16 e exhibit depths P m , Pe substantially identical, and in particular greater than the depths Pi of the internal cavities 16i.

Claims

DEMANDS 1. A bicycle fork crown, comprising a central part (1) in which is formed a central channel (2) for receiving a pivot (3) of said fork and, formed in one piece, two arms (4) extending laterally on either side of said central part, each of said arms having a distal portion (5) carrying a lateral channel (6) for receiving a leg (8) of said fork, said lateral and central channels extending along a vertical axis (V) each opening into orifices (2a, 2b, 6a, 6b) formed in the respectively upper (7a) and lower (7b) faces of said fork crown, said faces being separated by a thickness of material (E) measured along a vertical direction, said fork crown being characterized in that it has at least one cavity (16i, 16 m 16 e) which is arranged between two vertically opposed zones of respectively a face (7a, 7b), said cavity having an opening (17\, 17 m 17 e ) formed in one of said zones and extending over a depth (Pi, P m , Pe) measured along a vertical direction which is less than 80% of the thickness (E) between said zones.

2. Fork tee according to claim 1, characterized in that the cavity (16i, 16m, 16 e ) features a radial border (20) connecting with the opening (17i, 17m, 17 e ) and a well (21 i, 21 m 21 e ) whose periphery extends generally vertically to a bottom (22i, 22 m 22 e ).

3. Fork tee according to claim 2, characterized in that the bottom (22i, 22 m 22 e ) extends generally parallel to the area of ​​the opposite face (7a) so as to form a thickness (es, e m , e e) substantially constant between said background and said face.

4. Fork tee according to any one of claims 1 to 3, characterized in that the opening (17, 17 m 17 e ) of the cavity (16i, 16 m 16 e ) is formed in an area of ​​the lower face (7b).

5. A fork tee according to any one of claims 1 to 4, characterized in that the central conduit (2) has a vertical plane (T) of symmetry, said fork tee having two sets of cavities (16i, 16m, 16 e ) arranged on either side of said plan.

6. Fork tee according to claim 5, characterized in that it is symmetrical with respect to the vertical plane (T) of symmetry of the central conduit (2).

7. Fork tee according to any one of claims 5 or 6, characterized in that each assembly has an internal group of at least one cavity (16i) whose opening (17i) extends over the central part (1) and over the arm (4).

8. Fork tee according to claim 7, characterized in that the internal group comprises two cavities (16i) whose openings (17i) are separated along a transverse direction (D).

9. Fork tee according to claim 8, characterized in that the two cavities (16i) are symmetrical with respect to a longitudinal plane (L).

10. A fork tee according to any one of claims 5 to 9, characterized in that each assembly has a central group of at least one cavity (16m) whose opening (17 m ) is formed on the arm (4).

11. Fork tee according to claim 10, characterized in that the central group comprises a cavity (16 m ) whose opening (17 m) is positioned in the middle part of the arm (4).

12. A fork tee according to any one of claims 5 to 11, characterized in that each assembly has an external group of at least one cavity (16 e ) whose opening (17 e ) is formed on the arm (4) near the lateral conduit (6).

13. Fork tee according to claim 12, characterized in that the outer group comprises a cavity (16 e ) whose opening (17 e ) is positioned in the front part of the arm (4).

14. Fork tee according to any one of claims 1 to 13, characterized in that it is manufactured by pressure injection molding of an aluminum alloy.

15. Bicycle fork comprising a fork crown according to any one of claims 1 to 14, wherein a pivot (3) is fixed in the central channel (2) above the upper face (7a), and two legs (8) are fixed in respectively a lateral conduit (6) below the lower face (7b).

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